FEC on camera vs on transmitter vs on flash

Wilt wrote in post #19129838
I will disagree...when I set the FEC value on the camera (7DII), it does cause an immediate and viewable on-flash menu change in the FEC value of the flash!

And nevertheless, if your Canon flash behaves differently from my Metz flash with regard to the FEC seeting on flash, DOES alter the light output. I recently did a test because a 7DII owner could not get FEC to work.

• I adjusted FEC on camera by -2EV, 0EV, and +2EV with the flash at 0EV, and the expected change in output did occur (unlike the OP experience in that thread)
  

And regardless of the FEC value set on the flash, the end result is the same

• Camera FEC -2EV, 0EV, and +2EV with the flash menu set to FEC 0EV is identical in result to Camera FEC -2EV, 0EV, and +2EV with the flash menu set initially to FEC +1EV
  

IOW, the camera FEC setting does override the flash's FEC setting.

Sorry Wilt.
You are right if the 600 EX-RT is on Camera and you are changing the FEC from the back of Camera Body LCD. (On Camera Flash)
If using ST-E3 RT and one or more 600 EX-RT In Off Camera Flash, the FEC value +1.0 from Trasmitter will not correspond to the 600 Information screen, 0 FEC, however the FEC flash output will correspond.
FEC does work, the software will not reflect the changes in FEC in the Off Camera Flash Display, but changes in out put does.
And yes I did this again the old fashion way, the Human test.
My results are confirmed.
Would a software update be welcome to fix this little confusing situation? you bet.

Nick5 wrote in post #19129936
Sorry Wilt.
You are right if the 600 EX-RT is on Camera and you are changing the FEC from the back of Camera Body LCD. (On Camera Flash)
If using ST-E3 RT and one or more 600 EX-RT In Off Camera Flash, the FEC value +1.0 from Trasmitter will not correspond to the 600 Information screen, 0 FEC, however the FEC flash output will correspond.
FEC does work, the software will not reflect the changes in FEC in the Off Camera Flash Display, but changes in out put does.
And yes I did this again the old fashion way, the Human test.
My results are confirmed.
Would a software update be welcome to fix this little confusing situation? you bet.

Thanks, that is how we all come to have a more thorough understanding of how our stuff works (or doesn't)!
Nobody is necessarily wrong, they just don't necessarily cover all the bases. Just as my own Human testing disclosed behavior, but I don't own wireless transmitter to test that combination, so I omitted that configuation which you kindly added.

A bit like learning to spell in American English...you learn the basics, but then have to also learn all the exceptions.

OK, just tested on my setup - on camera transmitter, OCF.

Changing FEC on the transmitter changes the lighting as expected AND changes the indications on both transmitter AND OCF. But not on the camera's settings. That is now grayed out.

Changing FEC on the camera flashes as expected but does NOT change the indication on the transmitter OR OCF.

I believe I saw this before but both forgot and did not write it down and this is partly what prompted the original question of is there a difference where one chooses to control FEC.

rebop wrote in post #19129980
OK, just tested on my setup - on camera transmitter, OCF.

Changing FEC on the transmitter changes the lighting as expected AND changes the indications on both transmitter AND OCF. But not on the camera's settings. That is now grayed out.

Changing FEC on the camera flashes as expected but does NOT change the indication on the transmitter OR OCF.

I believe I saw this before but both forgot and did not write it down and this is partly what prompted the original question of is there a difference where one chooses to control FEC.

So, curious...

What happens if you set FEC +1EV on the transmitter, and try to set FEC -1EV via the camera control or menu? Does the camera setting override the setting you put on the transmitter? (the camera setting does override the setting on the flash when mounted in the hotshoe)

Wilt wrote in post #19129999
So, curious...

What happens if you set FEC +1EV on the transmitter, and try to set FEC -1EV via the camera control or menu? Does the camera setting override the setting you put on the transmitter? (the camera setting does override the setting on the flash when mounted in the hotshoe)

If set on transmitter, the option to change on the camera is grayed out.

Wilt wrote in post #19129999
So, curious...

What happens if you set FEC +1EV on the transmitter, and try to set FEC -1EV via the camera control or menu? Does the camera setting override the setting you put on the transmitter? (the camera setting does override the setting on the flash when mounted in the hotshoe)

There is no benefit at all to change the FEC from the 600 EX-RT in Off Camera Flash situations. Use the ST-E3 RT transmitter as it is on the camera with you. Your transmitter is the Primary control. Why walk around to an OCF to adjust, when the camera is with you. You will then know each OCF 600 EX-RT FEC amount all in one location with you on the Cameras ST-E3 RT. Use the benefit of Radio communication. K.I.S.S.